Temp probe bad

[aslmx]

I have a digital thermometer on my glass that's been there before I got my Apex. It's showing 74 and my Apex is showing 78. One of them is lying to me. Is their a way to check other than buying another thermometer to compare?

 

[Randy Holmes-Farley]

You could try putting both in icewater (32 deg F), if they go that low. That isn't perfect in terms of knowing accuracy at tank temps, but it might be helpful.